Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
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Question 573
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A many-to-one relationship exists between entity sets r1 and r2. How will it be represented using functional dependencies if Pk(r) denotes the primary key attribute of relation r?
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Pk(r1 ) → Pk(r2 )
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Pk(r2 ) → Pk(r1 )
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Pk(r2 ) → Pk(r1 ) and Pk(r1 ) → Pk(r2 )
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Pk(r2 ) → Pk(r1 ) or Pk(r1 ) → Pk(r2 )
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Question 573 Explanation:
Here we have a many to one relationship between between Set(r1) and set(r2).
→ Elements of set(r2) can’t identify elements of sert(r1) because one value element in set(r2) is pointing to more than one element of set(r1).
→ So we can’t say Pk(r2 ) → Pk(r1) but elements of set(r1) are pointing to exactly one element of set(r2) so we can say that Pk(r2 ) → Pk(r1 ) because r1 is uniquely identifying r2.
Correct Answer: A
Question 573 Explanation:
Here we have a many to one relationship between between Set(r1) and set(r2).
→ Elements of set(r2) can’t identify elements of sert(r1) because one value element in set(r2) is pointing to more than one element of set(r1).
→ So we can’t say Pk(r2 ) → Pk(r1) but elements of set(r1) are pointing to exactly one element of set(r2) so we can say that Pk(r2 ) → Pk(r1 ) because r1 is uniquely identifying r2.